U.S. patent number 7,896,465 [Application Number 12/240,840] was granted by the patent office on 2011-03-01 for inkjet printhead with a printer controller for controlling nozzle firing sequence.
This patent grant is currently assigned to Silverbrook Research Pty Ltd. Invention is credited to Brian Robert Brown, Kia Silverbrook, Simon Robert Walmsley.
United States Patent |
7,896,465 |
Brown , et al. |
March 1, 2011 |
Inkjet printhead with a printer controller for controlling nozzle
firing sequence
Abstract
An inkjet printhead includes a number of printhead modules
arranged end-to-end to span a width of a page, the printhead
modules defining color channels also to span the width of the page.
A plurality of inkjet nozzles is arranged on the modules such that
rows of the nozzles span the width of the page, with at least one
row of nozzles in fluid communication with respective channels, the
nozzles capable of being fired to eject ink from their associated
channels, the nozzles of each row on an associated module defining
a segment of nozzles. A printer controller controls a firing
sequence of the nozzles and is configured so that nozzles from
segments associated with different color channels are fired
sequentially during a predetermined time allocated for firing a
line of nozzles.
Inventors: |
Brown; Brian Robert (Balmain,
AU), Walmsley; Simon Robert (Balmain, AU),
Silverbrook; Kia (Balmain, AU) |
Assignee: |
Silverbrook Research Pty Ltd
(Balmain, New South Wales, AU)
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Family
ID: |
38118236 |
Appl.
No.: |
12/240,840 |
Filed: |
September 29, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090021547 A1 |
Jan 22, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11293798 |
Dec 5, 2005 |
7455376 |
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Current U.S.
Class: |
347/42; 347/13;
347/5 |
Current CPC
Class: |
B41J
29/393 (20130101); B41J 2/2139 (20130101) |
Current International
Class: |
B41J
2/155 (20060101) |
Field of
Search: |
;347/5,9,12,13,42,43 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0900656 |
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Mar 1999 |
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EP |
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0953451 |
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Nov 1999 |
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EP |
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1241006 |
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Sep 2002 |
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EP |
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0913255 |
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May 2003 |
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EP |
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1221372 |
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Jun 2005 |
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EP |
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2005041136 |
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Feb 2005 |
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JP |
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Primary Examiner: Nguyen; Lam S
Parent Case Text
This application is a continuation application of U.S. patent
application Ser. No. 11/293,798 filed on Dec. 5, 2005, now U.S.
Pat. No. 7,455,376, which is herein incorporated by reference.
Claims
The invention claimed is:
1. An inkjet printhead that comprises a number of printhead modules
arranged end-to-end to span a width of a page, the printhead
modules defining color channels in form of C1, C2, M1, M2 and Y
color channels, C1 and C2 being two respective cyan channels, M1
and M2 being two respective magenta channels and Y being a yellow
channel, also to span the width of the page; a plurality of inkjet
nozzles arranged on the modules such that rows of the nozzles span
the width of the page, with at least one row of nozzles in fluid
communication with respective channels, the nozzles capable of
being fired to eject ink from their associated channels, the
nozzles of each row on an associated module defining a segment of
nozzles; and a printer controller for controlling a firing sequence
of the nozzles, the printer controller being configured so that
nozzles from segments associated with different color channels are
fired sequentially during a predetermined time allocated for firing
a row of nozzles, and nozzles in each segment are arranged in
firing groups that fire sequentially over an allocated segment
time, wherein each of said ink color channels associates with two
rows of nozzles, the controller being configured to fire redundant
said two rows of nozzles such that never more than one out of every
two adjacent nozzles fire within a single nozzle row to modulate
peak power requirements of the printhead, and wherein the
controller being configured so that all different segments
associated with said color channels are fired in a firing time
allocated to one segment that is a fraction of time allocated for
firing a row of nozzles.
2. An inkjet printhead as claimed in claim 1, in which the
printhead modules are arranged to abut each other.
3. An inkjet printhead as claimed in claim 1, in which the nozzle
rows in each color channel are transversely offset with respect to
each other.
4. An inkjet printhead as claimed in claim 3, in which even and odd
nozzles in each color channel are transversely aligned with
respective even and odd nozzles in other color channels.
Description
FIELD OF THE INVENTION
This invention relates to a method of printing from an inkjet
printhead, whilst modulating a peak power requirement for the
printhead. It has been developed primarily to reduce the demands on
a pagewidth printhead power supply, although other advantages of
the methods of printing described herein will be apparent to the
person skilled in the art.
CO-PENDING APPLICATIONS
The following applications have been filed by the Applicant
simultaneously with the present application:
TABLE-US-00001 11/293,800 11/293,802 11/293,801 11/293,808
11/293,809 11/293,832 11/293,838 11/293,825 11/293,841 11/293,799
11/293,796 11/293,797 11/293,804 11/293,840 11/293,803 11/293,833
11/293,834 11/293,835 11/293,836 11/293,837 11/293,792 11/293,794
11/293,839 11/293,826 11/293,829 11/293,830 11/293,827 11/293,828
7,270,494 11/293,823 11/293,824 11/293,831 11/293,815 11/293,819
11/293,818 11/293,817 11/293,816 11/293,820 11/293,813 11/293,822
11/293,812 7,357,496 11/293,814 11/293,793 11/293,842 11/293,811
11/293,807 11/293,806 11/293,805 11/293,810
The disclosures of these co-pending applications are incorporated
herein by reference. The above applications have been identified by
their filing docket number, which will be substituted with the
corresponding application number, once assigned.
CROSS REFERENCES TO RELATED APPLICATIONS
Various methods, systems and apparatus relating to the present
invention are disclosed in the following US Patents/Patent
Applications filed by the applicant or assignee of the present
invention:
TABLE-US-00002 6,750,901 6,476,863 6,788,336 7,249,108 6,566,858
6,331,946 6,246,970 6,442,525 7,346,586 09/505,951 6,374,354
7,246,098 6,816,968 6,757,832 6,334,190 6,745,331 7,249,109
7,197,642 7,093,139 10/636,263 10/636,283 10/866,608 7,210,038
7,401,223 10/940,653 10/942,858 7,364,256 7,258,417 7,293,853
7,328,968 7,270,395 11/003,404 11/003,419 7,334,864 7,255,419
7,284,819 7,229,148 7,258,416 7,273,263 7,270,393 6,984,017
7,347,526 7,357,477 11/003,463 7,364,255 7,357,476 11/003,614
7,284,820 7,341,328 7,246,875 7,322,669 11/246,676 11/246,677
11/246,678 11/246,679 11/246,680 11/246,681 11/246,714 7,425,051
7,399,057 11/246,671 11/246,704 11/246,710 11/246,688 7,399,054
7,425,049 7,367,648 7,370,936 7,401,886 11/246,708 7,401,887
7,384,119 7,401,888 7,387,358 7,413,281 10/922,842 10/922,848
6,623,101 6,406,129 6,505,916 6,457,809 6,550,895 6,457,812
7,152,962 6,428,133 7,204,941 7,282,164 10/815,628 7,278,727
7,417,141 10/913,374 7,367,665 7,138,391 7,153,956 7,423,145
10/913,379 10/913,376 7,122,076 7,148,345 11/172,816 11/172,815
11/172,814 7,416,280 7,252,366 10/683,064 7,360,865 11/293,798
11/124,202 7,392,950 7,236,271 11/124,201 11/124,167 11/228,481
11/228,477 7,357,311 7,380,709 11/228,521 7,403,796 6,746,105
11/246,687 11/246,718 7,322,681 11/246,686 11/246,703 11/246,691
11/246,711 11/246,690 11/246,712 11/246,717 7,401,890 7,401,910
11/246,701 11/246,702 11/246,668 11/246,697 11/246,698 11/246,699
11/246,675 11/246,674 11/246,667 7,156,508 7,159,972 7,083,271
7,165,834 7,080,894 7,201,469 7,090,336 7,156,489 7,413,283
10/760,246 7,083,257 7,258,422 7,255,423 7,219,980 10/760,253
7,416,274 7,367,649 7,118,192 10/760,194 7,322,672 7,077,505
7,198,354 7,077,504 10/760,189 7,198,355 7,401,894 7,322,676
7,152,959 7,213,906 7,178,901 7,222,938 7,108,353 7,104,629
7,303,930 11/246,672 7,401,405 11/246,683 11/246,682 7,246,886
7,128,400 7,108,355 6,991,322 7,287,836 7,118,197 10/728,784
7,364,269 7,077,493 6,962,402 10/728,803 7,147,308 10/728,779
7,118,198 7,168,790 7,172,270 7,229,155 6,830,318 7,195,342
7,175,261 10/773,183 7,108,356 7,118,202 10/773,186 7,134,744
10/773,185 7,134,743 7,182,439 7,210,768 10/773,187 7,134,745
7,156,484 7,118,201 7,111,926 10/773,184 7,018,021 7,401,901
11/060,805 11/188,017 11/097,308 11/097,309 7,246,876 11/097,299
7,419,249 7,377,623 7,328,978 7,334,876 7,147,306 09/575,197
7,079,712 6,825,945 7,330,974 6,813,039 6,987,506 7,038,797
6,980,318 6,816,274 7,102,772 7,350,236 6,681,045 6,728,000
7,173,722 7,088,459 09/575,181 7,068,382 7,062,651 6,789,194
6,789,191 6,644,642 6,502,614 6,622,999 6,669,385 6,549,935
6,987,573 6,727,996 6,591,884 6,439,706 6,760,119 7,295,332
6,290,349 6,428,155 6,785,016 6,870,966 6,822,639 6,737,591
7,055,739 7,233,320 6,830,196 6,832,717 6,957,768 09/575,172
7,170,499 7,106,888 7,123,239 10/727,181 10/727,162 7,377,608
7,399,043 7,121,639 7,165,824 7,152,942 10/727,157 7,181,572
7,096,137 7,302,592 7,278,034 7,188,282 10/727,159 10/727,180
10/727,179 10/727,192 10/727,274 10/727,164 10/727,161 10/727,198
10/727,158 10/754,536 10/754,938 10/727,160 10/934,720 7,171,323
7,369,270 6,795,215 7,070,098 7,154,638 6,805,419 6,859,289
6,977,751 6,398,332 6,394,573 6,622,923 6,747,760 6,921,144
10/884,881 7,092,112 7,192,106 11/039,866 7,173,739 6,986,560
7,008,033 11/148,237 7,222,780 7,270,391 7,195,328 7,182,422
7,374,266 10/854,522 10/854,488 7,281,330 10/854,503 7,328,956
10/854,509 7,188,928 7,093,989 7,377,609 10/854,495 10/854,498
10/854,511 7,390,071 10/854,525 10/854,526 10/854,516 7,252,353
10/854,515 7,267,417 10/854,505 10/854,493 7,275,805 7,314,261
10/854,490 7,281,777 7,290,852 10/854,528 10/854,523 10/854,527
10/854,524 10/854,520 10/854,514 10/854,519 10/854,513 10/854,499
10/854,501 7,266,661 7,243,193 10/854,518 10/854,517 10/934,628
7,163,345 10/760,254 7,425,050 7,364,263 7,201,468 7,360,868
10/760,249 7,234,802 7,303,255 7,287,846 7,156,511 10/760,264
7,258,432 7,097,291 10/760,222 10/760,248 7,083,273 7,367,647
7,374,355 10/760,204 10/760,205 10/760,206 10/760,267 10/760,270
7,198,352 7,364,264 7,303,251 7,201,470 7,121,655 7,293,861
7,232,208 7,328,985 7,344,232 7,083,272 11/014,764 11/014,763
7,331,663 7,360,861 7,328,973 11/014,760 7,407,262 7,303,252
7,249,822 11/014,762 7,311,382 7,360,860 7,364,257 7,390,075
7,350,896 11/014,758 7,384,135 7,331,660 7,416,287 11/014,737
7,322,684 7,322,685 7,311,381 7,270,405 7,303,268 11/014,735
7,399,072 7,393,076 11/014,750 11/014,749 7,249,833 11/014,769
11/014,729 7,331,661 11/014,733 7,300,140 7,357,492 7,357,493
11/014,766 7,380,902 7,284,816 7,284,845 7,255,430 7,390,080
7,328,984 7,350,913 7,322,671 7,380,910 11/014,717 11/014,716
11/014,732 7,347,534 11/097,268 11/097,185 7,367,650
An application has been listed by its docket number. This will be
replaced when the application number is known. The disclosures of
these applications and patents are incorporated herein by
reference.
BACKGROUND TO THE INVENTION
Inkjet printers are now commonplace in homes and offices. For
example, inkjet photographic printers, which print color images
generated on digital cameras, are, to an increasing extent,
replacing traditional development of photographic negatives. With
the increasing use of inkjet printers, the demands of such printers
in terms of print quality and speed, continue to increase.
All commercially available inkjet printers use a scanning
printhead, which traverses across a stationary print medium. After
each sweep of the printhead, the print medium incrementally
advances ready for the next line(s) of printing. Such printers are
inherently slow and are becoming unable to meet the needs of
current demands of inkjet printers.
The present Applicant has previously described many different types
of pagewidth printheads, which are fabricated using MEMS
technology. In pagewidth printing, the print medium is continuously
fed past a stationary printhead, thereby allowing high-speed
printing at, for example, one page per 1-2 seconds. Moreover, MEMS
fabrication of the printhead allows a much higher nozzle density
than traditional scanning printheads, and print resolutions of 1600
dpi are possible.
Some of the Applicant's MEMS pagewidth printheads are described in
the patents and patent applications listed in the cross-references
section above, the contents of which are herein incorporated by
reference.
To a large extent, pagewidth printing has been made possible by
reducing the total energy required to fire each ink droplet and/or
efficiently removing heat from the printhead via ejected ink. In
these ways, self-cooling of the printhead can be achieved, which
enables a pagewidth printhead having a high nozzle density to
operate without overheating.
However, whilst a total amount of energy to print, say, a
full-color photographic page will be approximately constant for any
given pagewidth printhead, the power requirement of the printhead
may, of course, vary. An average power requirement for printing a
page is determined by the total energy required and the total time
taken to print the page, assuming an equal distribution of printing
over the time period. In addition, the power requirement of the
printhead during printing of the page may fluctuate. Due to a
particular configuration of the printhead or printer controller,
some lines of print may consume more power than other lines of
print. Hence, a peak power requirement for each line of printing
may be different.
In a typical pagewidth printhead, nozzles ejecting the same color
of ink are arranged longitudinally in color channels along the
length of the printhead. Each color channel may comprise one or
more rows of nozzles, all ejecting the same colored ink. In a
simple example, there may be one cyan row of nozzles, one magenta
row of nozzles and one yellow row of nozzles. Usually, each row of
nozzles will be fired sequentially during printing e.g. cyan then
magenta then yellow.
Furthermore, a typical pagewidth printhead may be comprised of a
plurality of printhead modules, which abut each other and cooperate
to form a printhead extending across a width of the page to be
printed. Each printhead module is typically a printhead integrated
circuit comprising nozzles and drive circuitry for firing the
nozzles. The rows of nozzles extend over the plurality of printhead
modules, with each printhead module including a respective segment
of each nozzle row.
In previous patent applications, listed below, we described various
types of printheads, printer controllers and methods of printing.
The contents of these patent applications are herein incorporated
by reference:
TABLE-US-00003 7,374,266 10/854,522 10/854,488 7,281,330 10/854,503
7,328,956 10/854,509 7,188,928 7,093,989 7,377,609 10/854,495
10/854,498 10/854,511 7,390,071 10/854,525 10/854,526 10/854,516
10/854,508 7,252,353 10/854,515 7,267,417 10/854,505 10/854,493
7,275,805 7,314,261 10/854,490 7,281,777 7,290,852 10/854,528
10/854,523 10/854,527 10/854,524 10/854,520 10/854,514 10/854,519
10/854,513 10/854,499 10/854,501 7,266,661 7,243,193 10/854,518
10/854,517 10/934,628 7,163,345
In our previous patent applications U.S. Ser. No. 10/854,498, filed
May 27, 2004, U.S. Ser. No. 10/854,516, filed May 27, 2004 and U.S.
Ser. No. 10/854,508, filed May 27, 2004, we described a method of
printing a line of dots where not all nozzles in one row or one
segment are fired simultaneously. Rather, the nozzles are fired
sequentially in firing groups in order to minimize the peak power
requirement during printing of one line. As a consequence, each
line of printing is typically not a perfectly straight line (unless
the physical arrangements of the nozzles directly compensates for
the firing order in which case it can be a straight line), although
this imperfection is undetectable to the human eye. Each segment on
a printhead module may comprise, for example, 10 firing groups of
nozzles, in order to minimize, as far as possible within the print
speed requirements, the peak power requirement for firing that
segment of the nozzle row.
In our previous patent applications U.S. Ser. No. 10/854,512, filed
May 27, 2004 and U.S. Ser. No. 10/854,491, filed May 27, 2004, we
described a means for joining abutting printhead modules such that
the effective distance between adjacent nozzles (`nozzle pitch`) in
the row remains constant. At one end of each printhead module,
there is a displaced nozzle row portion, which is not aligned with
its corresponding nozzle row. The firing of these displaced nozzles
is timed so that they effectively print onto the same line as the
row to which they correspond. As such, all references to "rows",
"rows of nozzles" or "nozzle rows" herein include nozzle rows
comprising one or more displaced row portions, as described in U.S.
Ser. No. 10/854,512, filed May 27, 2004 and U.S. Ser. No.
10/854,491, filed May 27, 2004.
In our previous patent applications U.S. Ser. No. 10/854,507, filed
May 27, 2004 and U.S. Ser. No. 10/854,523, filed May 27, 2004, we
described a means by which the visual effect of defective nozzles
is reduced. The printhead described comprises one or more
`redundant` color channels, so that for a first row of nozzles
ejecting a given color, there is a corresponding second
(`redundant`) row of nozzles from a different color channel which
eject the same color. As described in U.S. Ser. No. 10/854,507,
filed May 27, 2004 and U.S. Ser. No. 10/854,523, filed May 27,
2004, one line may be printed by the first nozzle row and the next
line is printed by the second nozzle row so that the first and
second nozzle rows print alternate lines on the page. Thus, if
there are unknown defective nozzles in a given row, the visual
effect on the page is halved, because only every other line is
printed using that row of nozzles.
Alternatively, if there are known dead nozzles in a given row, the
corresponding row of nozzles may be used to print dots in those
positions where there is a known dead nozzle. In other words, only
a small number of nozzles in the `redundant` row may be used to
print.
As already mentioned, the redundancy scheme described in U.S. Ser.
No. 10/854,507, filed May 27, 2004 and U.S. Ser. No. 10/854,523,
filed May 27, 2004 has the advantage of reducing the visual impact
of dead nozzles, either known or unknown. Moreover, careful choice
of redundant colors may be used to further reduce the visual impact
of dead nozzles. For example, since yellow makes the lowest
contribution (11%) to luminance, the human eye is least sensitive
to missing yellow dots and, therefore, yellow would be a poor
choice for a redundant color. On the other hand, black, makes a
much higher contribution to luminance and would be a good choice
for a redundant color.
However, while the redundancy scheme described in U.S. Ser. No.
10/854,507, filed May 27, 2004 and U.S. Ser. No. 10/854,523, filed
May 27, 2004 can compensate for dead nozzles and reduce (e.g.
halve) the number of dots fired by some nozzles, it places
increased demands on the power supply which is used to power the
printhead. The reason is because in the time it takes for the print
medium to advance by one line (one `line-time`), each nozzle row
must be allotted a portion of the line-time in which to fire, in
order to achieve dot-on-dot printing and provide the desired image.
Each nozzle row is allotted a portion of the line-time, since not
all nozzle rows can fire simultaneously. (If all nozzle rows were
to fire simultaneously, there would be an unacceptable current
overload of the printhead).
In a simple CMY pagewidth printhead, having three rows of nozzles
and no redundant color channels, each nozzle row must fire in
one-third of the line-time. If the average power requirement of the
printhead is x, then the peak power requirement over the duration
of the line-time is as shown in Table 1:
TABLE-US-00004 TABLE 1 Color Peak Power Line-time Channel
Requirement 0 C x 0.33 M x 0.67 Y x 0 (new line) C x . . . etc.
In this simple CMY printhead with no redundant nozzles, power is
distributed evenly over the duration of the line-time so that the
peak power requirement is constant and equal to the average power
requirement of the printhead. From the standpoint of the power
supply, this situation is optimal, but, on the other hand, there is
no means for minimizing the visual effects of dead nozzles.
In a CMY printhead having redundant cyan and magenta color channels
(i.e. C1, C2, M1, M2 and Y color channels) and a pair of nozzle
rows in each color channel (for even and odd dots), each nozzle row
is allotted one-tenth of the line-time, since there are now ten
nozzle rows. Now if the average power requirement of the printhead
is x, with the redundancy scheme and firing sequence described in
U.S. Ser. No. 10/854,507, filed May 27, 2004 and U.S. Ser. No.
10/854,523, filed May 27, 2004, the peak power requirement over the
duration of two line-times is as shown in Table 2:
TABLE-US-00005 TABLE 2 Color Peak Power Line-time Channel
Requirement 0 C1 (even) 1.67x 0.1 C2 (even) 0 0.2 M1 1.67x (even)
0.3 M2 0 (even) 0.4 Y (even) 1.67x 0.5 C1 (odd) 1.67x 0.6 C2 (odd)
0 0.7 M1 (odd) 1.67x 0.8 M2 (odd) 0 0.9 Y (odd) 1.67x 0 (new line)
C1 (even) 0 0.1 C2 (even) 1.67x 0.2 M1 0 (even) 0.3 M2 1.67x (even)
0.4 Y (even) 1.67x 0.5 C1 (odd) 0 0.6 C2 (odd) 1.67x 0.7 M1 (odd) 0
0.8 M2 (odd) 1.67x 0.9 Y (odd) 1.67x 0 (new line) C1 (even) 1.67x .
. . etc
It is evident from the above table that the peak power requirement
of the printhead fluctuates severely between 1.67x and 0 within the
period of a line-time, even though the average power consumed over
the whole line-time is still x. In practical terms, it is difficult
to manufacture a power supply which is able to deliver severely
fluctuating amounts of power within each line-time. Hence, the
redundancy described in U.S. Ser. No. 10/854,507, filed May 27,
2004 and U.S. Ser. No. 10/854,523, filed May 27, 2004 is difficult
to implement in practice, even though it offers considerable
advantages in terms of reducing the visual effects of known dead
nozzles.
Of course, a printhead could be configured not to fire redundant
color channels in a given line-time, resulting in an average of x
peak power for each nozzle row. Such a configuration is effectively
the same as that described in Table 1. While this configuration
would address peak power and misdirectionality issues, it would not
address the problem of known dead nozzles, since only one of each
redundant color channel would be able to be fired in a given
line-time, thereby losing one of the major advantages of
redundancy.
It would be desirable to provide a method of printing whereby
fluctuations in a peak power requirement are minimized. It would be
further desirable to provide a method of printing whereby the
average power requirement of the printhead is substantially equal
to the peak power requirement at any given time during printing. It
would be further desirable to provide a method of printing,
whereby, in addition minimizing fluctuating peak power
requirements, the visual effects of dead or malfunctioning nozzles
are reduced. It would be further desirable to provide a method of
printing, whereby, in addition to minimizing fluctuating peak power
requirements, the visual effects of misdirected ink droplets is
reduced.
SUMMARY OF THE INVENTION
In a first aspect, there is provided a method of modulating a peak
power requirement of an inkjet printhead, said printhead comprising
a plurality of first nozzles and a plurality of second nozzles
supplied with a same colored ink, said first nozzles and second
nozzles being configured in a plurality of sets, wherein each set
of nozzles comprises one first nozzle and one corresponding second
nozzle, each nozzle in a set being configurable to print a dot of
said ink onto a substantially same position on a print medium, said
method comprising:
(a) selecting a firing nozzle from at least one set of nozzles,
said selection being on the basis of modulating said peak power
requirement; and
(b) printing dots onto said print medium using said firing
nozzle.
In a second aspect, there is provided a method of printing a line
of dots from an inkjet printhead, said printhead comprising a
plurality of first nozzles and a plurality of second nozzles
supplied with a same colored ink, said first nozzles and second
nozzles being configured in a plurality of sets, wherein each set
of nozzles comprises one first nozzle and one corresponding second
nozzle, each nozzle in a set being configurable to print a dot of
said ink onto a substantially same position on a print medium,
said method comprising printing a line of dots across said print
medium such that said first nozzles and said second nozzles each
contribute dots to said line.
In a third aspect, there is provided a method of modulating a peak
power requirement of an inkjet printhead, said printhead comprising
a plurality of transversely aligned color channels, each color
channel comprising at least one nozzle row extending longitudinally
along said printhead, each nozzle in a color channel ejecting the
same colored ink, wherein said printhead is comprised of a
plurality of printhead modules, each printhead module comprising a
respective segment of each nozzle row,
said method comprising each of said printhead modules firing a
respective segment within a predetermined segment-time, wherein at
least one of said fired segments is contained in a different color
channel from at least one other of said fired segments.
In a fourth aspect, there is provided an inkjet printhead
comprising a plurality of transversely aligned color channels, each
color channel comprising at least one nozzle row extending
longitudinally along said printhead, each nozzle in a row ejecting
the same colored ink, wherein said printhead is comprised of a
plurality of printhead modules, and the number of color channels is
equal to the number of printhead modules.
In a fifth aspect, there is provided a printer controller for
supplying dot data to an inkjet printhead, said printhead
comprising a plurality of first nozzles and a plurality of second
nozzles supplied with a same colored ink, said first nozzles and
second nozzles being configured in a plurality of sets, wherein
each set of nozzles comprises one first nozzle and one
corresponding second nozzle, each nozzle in a set being
configurable by said printer controller to print a dot of said ink
onto a substantially same position on a print medium, said printer
controller being programmed to supply dot data such that said first
nozzles and said second nozzles each contribute dots to a line of
printing.
In a sixth aspect, there is provided a printer controller for
supplying dot data to a printhead, said printhead comprising a
plurality of transversely aligned color channels, each color
channel comprising at least one nozzle row extending longitudinally
along said printhead, each nozzle in a color channel ejecting the
same colored ink, wherein said printhead is comprised of a
plurality of printhead modules, each printhead module comprising a
respective segment of each nozzle row, said printer controller
being programmed to supply dot data such that each of said
printhead modules fires a respective segment within a predetermined
segment-time, wherein at least one of said fired segments is
contained in a different color channel from at least one other of
said fired segments.
In a seventh aspect of the invention, there is provided a printhead
system comprising an inkjet printhead and a printer controller for
supplying dot data to said printhead,
said printhead comprising a plurality of first nozzles and a
plurality of second nozzles supplied with a same colored ink, said
first nozzles and second nozzles being configured in a plurality of
sets, wherein each set of nozzles comprises one first nozzle and
one corresponding second nozzle, each nozzle in a set being
configurable by said printer controller to print a dot of said ink
onto a substantially same position on a print medium,
said printer controller being programmed to supply dot data such
that said first nozzles and said second nozzles each contribute
dots to a line of printing.
In an eighth aspect of the invention, there is provided a printhead
system comprising an inkjet printhead and a printer controller for
supplying dot data to said printhead,
said printhead comprising a plurality of transversely aligned color
channels, each color channel comprising at least one nozzle row
extending longitudinally along said printhead, each nozzle in a
color channel ejecting the same colored ink, wherein said printhead
is comprised of a plurality of printhead modules, each printhead
module comprising a respective segment of each nozzle row,
said printer controller being programmed to supply dot data such
that each of said printhead modules fires a respective segment
within a predetermined segment-time, wherein at least one of said
fired segments is contained in a different color channel from at
least one other of said fired segments.
All aspects of the invention provide the advantage of modulating a
peak power requirement of the inkjet printhead. The corollary is
that a power supply, which supplies power to the printhead, need
not be specially adapted to supply severely fluctuating amounts of
power throughout each print cycle. In the present invention, the
degree of peak power fluctuations within each line-time are
substantially reduced. Hence, the design and manufacture of the
printhead power supply may be simplified and the power supply is
made more robust by virtue of not having to deliver severely
fluctuating amounts of power to the printhead.
In addition to modulating the peak power requirement of the
printhead, the present invention allows print quality to be
improved by using redundant nozzle rows, and without compromising
the above-mentioned improvements in peak power requirement. Print
quality may be improved by, for example, reducing the visual
effects of unknown dead nozzles in the printhead, and reducing the
visual effects of misdirected ink droplets.
As used herein, the terms "row", "rows of nozzles", "nozzle row"
etc. may include nozzle rows comprising one or more displaced row
portions.
As used herein, the term "ink" includes any type of ejectable
fluid, including, for example, IR inks and fixatives, as well as
standard CMYK inks. Likewise, references to "same colored ink"
include inks of a same color or type e.g. same cyan ink, same IR
ink or same fixative.
As used herein, the term "substantially the same position on a
print medium" is used to mean that a droplet of ink has an intended
trajectory to print at a same position on the print medium (as
another droplet of ink). However, due to inherent error margins in
firing droplets of ink, random misdirects or persistent misdirects,
a droplet of ink may not be printed exactly on its intended
position on the print medium. Hence, the term "substantially the
same position on a print medium" includes misplaced droplets, which
are intended to print at the same position, but may not necessarily
print at that position.
In accordance with some forms of the invention, the first nozzles
and second nozzles are configured in a plurality of sets, wherein
each set of nozzles comprises one first nozzle and one
corresponding second nozzle. Further, each nozzle in a set is
configurable to print a dot of ink onto a substantially same
position on a print medium, so that the nozzles can be used
interchangeably.
Optionally, a set is a pair of nozzles consisting of one first
nozzle and one second nozzle. However, a set may alternatively
comprise further (e.g. third and fourth) nozzles, with each nozzle
in the set being configurable to print a dot of ink onto a
substantially same position on a print medium. In other words, the
present invention is not limited to two rows of redundant nozzles
and may include, for example, three or more rows of redundant
nozzles.
Preferably, the printhead is a stationary pagewidth printhead and
the print medium is fed transversely past the printhead. The
present invention has been developed primarily for use with such
pagewidth printheads.
Optionally, the printhead comprises a plurality of transversely
aligned color channels, each color channel comprising at least one
nozzle row extending longitudinally along the printhead, each
nozzle in a color channel ejecting the same colored ink. As
described in more detail below, each transversely aligned color
channel is allotted a portion of a line-time for firing. In this
way, dot-on-dot printing can be achieved, which is optimal for
dithering.
Color channels in the printhead may eject the same or different
colored inks. However, all nozzles in the same color channel are
typically supplied with and eject the same colored ink. Color
channels ejecting the same colored ink are sometimes termed
`redundant` color channels. Typically, the printhead comprises at
least one redundant color channel so that at least one color
channel ejects the same colored ink as at least one other color
channel.
Each color channel may comprise a plurality of nozzle rows.
Optionally, each color channel comprises a pair of nozzle rows.
Typically, nozzle rows in the same color channel are transversely
offset from each other. For example, one nozzle row in a pair may
be configured to print even dots on a line, while the other nozzle
row in the pair may be configured to print odd dots on the same
line. The nozzle rows in a pair are usually spaced apart in a
transverse direction to allow convenient timing of nozzle firings.
For example, the even and odd nozzle rows in one color channel may
be spaced apart by two lines of printing.
Optionally, each set of nozzles comprises one first nozzle from a
first color channel and one second nozzle from a second color
channel. The first and second nozzles in the set are aligned
transversely so that each can print onto the substantially same
position on a print medium.
Optionally, one set of nozzles prints a column of same-colored dots
down a print medium, with each nozzle in the set contributing dots
to the column. As used herein, a "column" refers to a line of dots
printed substantially perpendicular to the printhead and
substantially parallel with a feed direction of the print medium.
Optionally, one first nozzle in the set prints about half of the
column and one second nozzle in the set prints about half of the
column, so that the first and second nozzles in the set share
printing of the column equally between them.
Optionally, a visual effect of misdirected ink droplets is reduced.
An advantage of using a plurality (e.g. two) nozzles for printing
the same column is that misdirected ink droplets may be averaged
out between those nozzles.
Optionally, when printing a line of same-colored dots across the
print medium, the first nozzles and second nozzles contribute dots
to the line. As used herein, a "line" refers to a line of dots
printed substantially parallel with the printhead and substantially
perpendicular to a feed direction of the print medium. Optionally,
the first nozzles print about half of the line and the second
nozzles print about half of the line, so that the first and second
nozzles share printing of the line equally between them.
Accordingly, the peak power requirement for printing the line is
reduced by about 50%, as compared to printing the line using only
first nozzles or only second nozzles. Optionally, alternate first
nozzles in a first nozzle row are used to print about half of the
line and alternate second nozzles in a second nozzle row are used
to print about half of the line. However, other patterns for
sharing printing between the first and second nozzles may also be
used.
Optionally, a visual effect of malfunctioning or dead nozzles is
reduced. The nozzles may be known dead nozzles or unknown dead
nozzles. The visual effect of an unknown dead nozzle is reduced by
virtue of the fact that the nozzle is only required to print about
half of the time. For example, with an unknown dead magenta nozzle,
a column of magenta dots would be missing completely with no
redundancy, whereas half of the column is still printed using
redundancy. The latter is, of course, far more visually acceptable
than the former.
Optionally, the color (which is the same color printed by the first
and second nozzles) is magenta, cyan or black. The human eye is
most sensitive to magenta, cyan and black, and these colors are
consequently the preferred candidates for redundancy. A printhead
may contain more than one redundant color channels. For example,
the printhead may comprise first and second magenta nozzles, and
first and second cyan nozzles.
In accordance with some forms of the invention, there is provided a
method of out-of-phase printing so as to modulate a peak power
requirement of the printhead. Typically, the printhead comprises a
plurality of transversely aligned color channels with each color
channel comprising at least one nozzle row extending
longitiudinally along the printhead. Each nozzle in a color channel
is supplied with and ejects the same colored ink. Typically, the
printhead is comprised of a plurality of printhead modules, with
each module comprising a respect segment of each nozzle row.
Out-of-phase printing is provided by a method in which each of the
printhead modules fires a respective segment within a predetermined
segment-time, wherein at least one of the fired segments is
contained in a different color channel from at least one other of
the fired segments.
A segment-time may be defined as a predetermined fraction of one
line-time. A line-time is defined as the time taken for the print
medium to advance past the printhead by one line. Typically, all
segments in a nozzle row are fired within one line-time.
Optionally, a segment-time is equal to one line-time divided by the
number of nozzle rows. However, a period of each line-time may be
dedicated to a line-based overhead, in which case the segment-time
will be less than one line-time divided by the number of nozzle
rows. Generally, all segment-times are equal.
Optionally, at least one nozzle row has a different peak power
requirement from other nozzle rows. For example, a redundant nozzle
row would normally have half the peak power requirement of a
non-redundant nozzle row. Optionally, a predetermined firing
sequence modulates the peak power requirement during each
segment-time so that the peak power requirement is within about
10%, optionally within 5%, of the average power requirement of the
printhead. In some embodiments of the invention, the peak power
requirement of the printhead is equal to the average power
requirement of the printhead.
Typically, all segments on the printhead are fired within one-line
time.
In some forms of the invention, the number of color channels is
equal to the number of printhead modules. This is the optimum
number of color channels and modules to achieve perfect
out-of-phase firing. However, as will be explained in more detail
below, the advantages of out-of-phase firing may still be achieved
using any number of printhead modules and color channels.
Optionally, with equal numbers of modules and color channels, each
of the printhead modules fires a segment from a different color
channel within the predetermined segment-time. Further, each
segment in a nozzle row may be fired sequentially. However, as will
be explained in more detail below, each segment in a nozzle row
need not be fired sequentially, whilst still enjoying the
advantages of out-of-phase firing.
BRIEF DESCRIPTION OF THE DRAWINGS
Specific forms of the present invention will be now be described in
detail, with reference to the following drawings, in which:
FIG. 1 is a plan view of a pagewidth printhead according to the
invention;
FIG. 2 is a plan view of a printhead module, which is a part of the
printhead shown in FIG. 1;
FIG. 3 is a schematic representation of a portion of each color
channel of the printhead shown in FIG. 1;
FIG. 4A shows which even nozzles fire in one line-time using
dot-at-a-time redundancy according to the invention;
FIG. 4B shows which odd nozzles fire in the next line-time from
FIG. 4A; and
FIG. 5 shows a printhead system according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described with reference to a CMY pagewidth
inkjet printhead 1, as shown in FIG. 1. The printhead 1 has five
color channels 2, 3, 4, 5 and 6, which are C1, C2, M1, M2 and Y
respectively. In other words cyan and magenta have `redundant`
color channels. The reason for making C and M redundant is that Y
only contributes 11% of luminance, while C contributes 30% and M
contributes 59%. Since the human eye is least sensitive to yellow,
it is more visually acceptable to have missing yellow dots than
missing cyan or magenta dots. In this printhead, black (K) printing
is achieved via process-black (CMY).
The printhead 1 is comprised of five abutting printhead modules 7,
which are referred to from left to right as A, B, C, D and E. The
five modules 7 cooperate to form the printhead 1, which extends
across the width of a page (not shown) to be printed. In this
example, each module 7 has a length of about 20 mm so that the five
abutting modules form a 4'' printhead, suitable for pagewidth
4''.times.6'' color photo printing. During printing, paper is fed
transversely past the printhead 1 and FIG. 1 shows this paper
direction.
Each of the five color channels on the printhead 1 comprises a pair
of nozzle rows. For example, the C1 color channel 2 comprises
nozzle rows 2a and 2b. These nozzle rows 2a and 2b extend
longitudinally along the whole length of the printhead 1. Where
abutting printhead modules 7 are joined, there is a displaced (or
dropped) triangle 8 of nozzle rows. These dropped triangles 8 allow
printhead modules 7 to be joined, whilst effectively maintaining a
constant nozzle pitch along each row. A timing device (not shown)
is used to delay firing nozzles in the dropped triangles 8, as
appropriate. A more detailed explanation of the operation of the
dropped triangle 8 is provided in the Applicant's patent
applications U.S. Ser. No. 10/854,512, filed May 27, 2004 and U.S.
Ser. No. 10/854,491, filed May 27, 2004.
Each of the printhead modules 7 contains a segment from each of the
nozzle rows. For example, printhead module A contains segments
2a.sup.A, 2b.sup.A, 3a.sup.A, 3b.sup.A, 4a.sup.A etc. Segments from
the same nozzle row cooperate to form a complete nozzle row. For
example, segments 2a.sup.A, 2a.sup.B, 2a.sup.C, 2a.sup.D and
2a.sup.E cooperate to form nozzle row 2a. FIG. 2 shows the
printhead module A with its respect segments from each nozzle
row.
Referring to FIG. 3, there is shown a detailed schematic view of a
portion of the five color channels 2, 3, 4, 5 and 6. From FIG. 3,
it can be seen that the pair of nozzle rows (e.g. 2a and 2b) in
each color channel (e.g. 2) are transversely offset from each
other. In color channel 2, for example, nozzle row 2a prints even
dots in a line, while nozzle row 2b prints interstitial odd dots in
a line.
Furthermore, the even rows of nozzles 2a, 3a, 4a, 5a and 6a are
transversely aligned, as are the odd rows of nozzles 2b, 3b, 4b, 5b
and 6b. This transverse alignment of the five color channels allows
dot-on-dot printing, which is optimal in terms of dithering. Within
a period of one line-time, all even nozzles and all odd nozzles
must be fired so that dot-on-dot printing is achieved. The even and
odd nozzles (e.g. 2a and 2b) in the same color channel (e.g. 2) may
be separated by, for example, two lines. Adjacent color channels
(e.g. 2 and 3) may be separated by, for example, ten lines.
However, it will be appreciated that the exact spacing between
even/odd nozzle rows and adjacent color channels may be varied,
whilst still achieving dot-on-dot printing.
Dot-at-a-Time Redundancy
In the printhead 1 described above, there are two cyan (C1, C2) and
two magenta (M1, M2) color channels. In the Applicant's
terminology, the C1/C2 and M1/M2 color channels are described as
`redundant` color channels.
As explained above, with five color channels and a pair of nozzle
rows in each color channel, each nozzle row must print in one-tenth
of the line-time in order to achieve all the advantages of
redundancy and compensate for any known dead nozzles using a
redundant color channel. The inherent power supply problems in
relation to the redundancy scheme described in U.S. Ser. No.
10/854,507, filed May 27, 2004 and U.S. Ser. No. 10/854,523, filed
May 27, 2004 have also been described above.
Dot-at-a-time redundancy is where redundant rows of nozzles are
used such that there is never more than one out of every two
adjacent nozzles firing within a single nozzle row. In other words,
the even dots for a color are produced by two nozzle rows (each
printing half of the even dots), and the odd dots for a color are
produced by two nozzle rows (each printing half of the dots). For
example, nozzle rows 2a and 3a may both contribute even dots to a
line of printing, and nozzle rows 2b and 3b may both contribute odd
dots to a line of printing.
FIGS. 4A and 4B show a firing sequence for two lines of printing
using dot-at-a-time redundancy. The nozzles indicated in FIGS. 4A
and 4B are not fired simultaneously; each nozzle row is allotted
one-tenth of the line-time in which to fire its nozzles, with even
nozzles rows firing sequentially followed by odd nozzle rows firing
sequentially.
Referring to FIG. 4A, in the first line-time alternate nozzles are
fired in each nozzle row from the C1, C2, M1 and M2 color channels.
Nozzles fired from C2 and M2 complement those fired from C1 and M1.
For example, alternate even nozzles are fired from nozzle row 2a
and complementary alternate even nozzles are fired from nozzle row
3a. Nozzle rows 6a and 6b in the Y channel have no redundancy and
each of these nozzle rows must therefore fire all its nozzles in
one-tenth of the line-time.
Referring to FIG. 4B, in the second line-time the alternate nozzles
fired in the first line-time are inversed.
By using this dot-at-a-time redundancy scheme, print quality is
improved by reducing misdirection artifacts (thereby maximizing
dot-on-dot placement) and reducing the visual effect of unknown
dead nozzles. For example, if half of the dots in a column are from
an operational nozzle and half are from a dead nozzle, the visual
effect of the dead nozzle will be reduced and the effective print
quality is greater than if the entire column came from the dead
nozzle. In other words, the present invention achieves at least as
good print quality as the line-at-a-time redundancy described in
U.S. Ser. No. 10/854,507, filed May 27, 2004 and U.S. Ser. No.
10/854,523, filed May 27, 2004.
Moreover, the peak power requirements of the printhead are
modulated during printing of each line, so that the peak power
requirements do not fluctuate as severely as in Table 2. Table 3
shows how the peak power requirement of the printhead (having an
average power requirement of x) varies over two lines of printing
using dot-at-a-time redundancy according to the present
invention:
TABLE-US-00006 TABLE 3 Color Nozzle Peak Power Line-time Channel
Row Requirement 0 2 (C1) 2a (even) 0.83x 0.1 3 (C2) 3a (even) 0.83x
0.2 4 (M1) 4a (even) 0.83x 0.3 5 (M2) 5a (even) 0.83x 0.4 6 (Y) 6a
(even) 1.67x 0.5 2 (C1) 2b (odd) 0.83x 0.6 3 (C2) 3b (odd) 0.83x
0.7 4 (M1) 4b (odd) 0.83x 0.8 5 (M2) 5b (odd) 0.83x 0.9 6 (Y) 6b
(odd) 1.67x 0 (new line) 2 (C1) 2a (even) 0.83x 0.1 3 (C2) 3a
(even) 0.83x 0.2 4 (M1) 4a (even) 0.83x 0.3 5 (M2) 5a (even) 0.83x
0.4 6 (Y) 6a (even) 1.67x 0.5 2 (C1) 2b (odd) 0.83x 0.6 3 (C2) 3b
(odd) 0.83x 0.7 4 (M1) 4b (odd) 0.83x 0.8 5 (M2) 5b (odd) 0.83x 0.9
6 (Y) 6b (odd) 1.67x 0 (new line) 2 (C1) 2a (even) 0.83x . . .
etc
It is evident from Table 3 that the fluctuations in peak power
requirement are fewer and less severe compared to line-at-a-time
redundancy, described in Table 2. In terms of the design of the
printhead power supply, dot-at-a-time redundancy according to the
present invention offers significant advantages over line-at-a-time
redundancy, whilst maintaining the same improvements in print
quality.
Out-of-Phase Firing
In all the firing sequences described so far, each color channel is
fired in-phase--that is, a whole row of, say, even nozzles from one
color channel is fired within its allotted portion of the
line-time. In-phase firing provides simpler programming of the
printer controller, which controls the firing sequence via dot data
sent to the printhead 1.
However, according to another form of the present invention, the
firing may be out-of-phase--that is, within the same allotted
portion of the line-time (termed the `segment-time`), at least one
segment of nozzles is fired from a color channel that is different
from at least one other segment of nozzles. With appropriate
sequencing of segment firings, a whole nozzle row can be fired
within one line-time, such that the net result is effectively the
same as in-phase firing.
In the case of the printhead 1, having five color channels and five
segments in each nozzle row, it possible to fire segments from all
different color channels within one segment time (i.e. one-tenth of
a line-time). Segments contained in the same nozzle row are,
therefore, fired sequentially during one line-time.
A major advantage of out-of-phase firing is that if one or more
color channels (e.g. Y) has a different peak power requirement to
the other color channels, this difference is averaged into the
power requirements of the other color channels within each
segment-time. Hence, the spike in power (corresponding to the Y
channel) in Table 3 is effectively merged into rest of the
line-time. The result is that the peak power requirement during
each segment-time is always equal to the average power requirement
for the printhead. This situation is optimal for supplying power to
the printhead.
Table 4 illustrates a sequence of out-of-phase firing for one line
of printing from the printhead 1, using dot-at-a-time
redundancy.
TABLE-US-00007 TABLE 4 Module A Module B Module C Module D Module E
Peak Power Line-time (CC, S, P) (CC, S, P) (CC, S, P) (CC, S, P)
(CC, S, P) Requirement 0 C1, 2a.sup.A, C2, 3a.sup.B, M1, 4a.sup.C,
M2, 5a.sup.D, Y, 6a.sup.E, x 0.83x 0.83x 0.83x 0.83x 1.67x 0.1 C2,
3a.sup.A, M1, 4a.sup.B, M2, 5a.sup.C, Y, 6a.sup.D, C1, 2a.sup.E, x
0.83x 0.83x 0.83x 1.67x 0.83x 0.2 M1, 4a.sup.A, M2, 5a.sup.B, Y,
6a.sup.C, C1, 2a.sup.D, C2, 3a.sup.E, x 0.83x 0.83x 1.67x 0.83x
0.83x 0.3 M2, 5a.sup.A, Y, 6a.sup.B, C1, 2a.sup.C, C2, 3a.sup.D,
M1, 4a.sup.E, x 0.83x 1.67x 0.83x 0.83x 0.83x 0.4 Y, 6a.sup.A, C1,
2a.sup.B, C2, 3a.sup.C, M1, 4a.sup.D, M2, 5a.sup.E, x 1.67x 0.83x
0.83x 0.83x 0.83x 0.5 C1, 2b.sup.A, C2, 3b.sup.B, M1, 4b.sup.C, M2,
5b.sup.D, Y, 6b.sup.E, x 0.83x 0.83x 0.83x 0.83x 1.67x 0.6 C2,
3b.sup.A, M1, 4b.sup.B, M2, 5b.sup.C, Y, 6b.sup.D, C1, 2b.sup.E, x
0.83x 0.83x 0.83x 1.67x 0.83x 0.7 M1, 4b.sup.A, M2, 5b.sup.B, Y,
6b.sup.C, C1, 2b.sup.D, C2, 3b.sup.E, x 0.83x 0.83x 1.67x 0.83x
0.83x 0.8 M2, 5b.sup.A, Y, 6b.sup.B, C1, 2b.sup.C, C2, 3b.sup.D,
M1, 4b.sup.E, x 0.83x 1.67x 0.83x 0.83x 0.83x 0.9 Y, 6b.sup.A, C1,
2b.sup.B, C2, 3b.sup.C, M1, 4b.sup.D, M2, 5b.sup.E, x 1.67x 0.83x
0.83x 0.83x 0.83x 0 (new C1, 2a.sup.A, C2, 3a.sup.B, M1, 4a.sup.C,
M2, 5a.sup.D, Y, 6a.sup.E, x line) 0.83x 0.83x 0.83x 0.83x 1.67x
... etc CC = Color Channel; S = Segment; P = Peak Power
Requirement
It should be remembered that, even within one segment, not all
nozzles fire simultaneously. The nozzles in one segment are
arranged in firing groups, which fire sequentially over the course
of their allotted segment-time. However, the important point is
that at any given instant, some C1, C2, M1, M2 and Y nozzles will
fire simultaneously, thereby averaging out the higher peak power
requirement of the yellow nozzle row.
In the case of five printhead modules and five color channels, it
can be seen that out-of-phase firing works out well. Segments from
each color channel can be rotated so that all different segments
are fired in one segment-time.
However, it will be appreciated that out-of-phase firing also works
well with any number of printhead modules or color channels. For
example, using 20 mm printhead modules 7, an A4 pagewidth printhead
is comprised of eleven abutting modules [(i) to (xi)]. With five
color channels and eleven printhead modules, it is impossible to
ensure that each printhead module fires a different color channel
within a segment-time (i.e. one-tenth of a line-time). Regardless,
out-of-phase firing can still be used to optimize the peak power
requirement of the printhead.
For example, the A4 pagewidth printhead may have C, M, Y, K1 and K2
color channels. Since there are redundant K channels, these nozzle
rows will have a lower peak power requirement than the C, M and Y
channels using dot-at-a-time redundancy. Using in-phase firing,
there would be appreciable peak power fluctuations during each
line-time (C=1.25x, M=1.25x, Y=1.25x, K1=0.625x, K2=0.625x).
However, it can be seen from Table 5 that out-of-phase firing
accommodates the eleven printhead modules and provides a peak power
requirement that is always within 10% of the average power
requirement x of the printhead. Indeed, the peak power requirement
is always within 5% of the average power requirement x in this
example. For the purposes of providing a power supply for the
printhead, such small variations in peak power requirement during
each line-time are not significant and would not affect the design
of the power supply.
TABLE-US-00008 TABLE 5 t (i) (ii) (iii) (iv) (v) (vi) (vii) (viii)
(ix) (x) (xi) P 0 C(e) M(e) Y(e) K1(e) K2(e) C(e) M(e) Y(e) K1(e)
K2(e) C(e) 1.023x 0.1 M(e) Y(e) K1(e) K2(e) C(e) M(e) Y(e) K1(e)
K2(e) C(e) M(e) 1.023x 0.2 Y(e) K1(e) K2(e) C(e) M(e) Y(e) K1(e)
K2(e) C(e) M(e) Y(e) 1.023x 0.3 K1(e) K2(e) C(e) M(e) Y(e) K1(e)
K2(e) C(e) M(e) Y(e) K1(e) 0.966x 0.4 K2(e) C(e) M(e) Y(e) K1(e)
K2(e) C(e) M(e) Y(e) K1(e) K2(e) 0.966x 0.5 C(o) M(o) Y(o) K1(o)
K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) 1.023x 0.6 M(o) Y(o) K1(o)
K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) M(o) 1.023x 0.7 Y(o) K1(o)
K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) M(o) Y(o) 1.023x 0.8 K1(o)
K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) M(o) Y(o) K1(o) 0.966x 0.9
K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) M(o) Y(o) K1(o) K2(o) 0.966x
0 C(o) M(o) Y(o) K1(o) K2(o) C(o) M(o) Y(o) K1(o) K2(o) C(o) 1.023x
t = line-time; P = Peak Power Requirement (e) = even rows of
nozzles; (o) = odd rows of nozzles
From the foregoing it will be appreciated that the combination of
out-of-phase firing together with dot-at-a-time redundancy is
optimal for achieving excellent print quality and an acceptable
power requirement for the printhead during printing.
However, these methods of printing may equally be used
individually, providing their inherent advantages, or in
combination with other methods of printing. For example,
out-of-phase firing or dot-at-a-time redundancy may be used in
combination with printhead module misplacement correction and/or
dead nozzle compensation, as described in our earlier patent
applications U.S. Ser. No. 10/854,521 filed May 27, 2004 and U.S.
Ser. No. 10/854,515, filed May 27, 2004.
Printer Controller
It will also be appreciated by the skilled person that a printer
controller 10, shown schematically in FIG. 5, may be suitably
programmed to provide dot data to the printhead 1, so as to print
in accordance with the methods described above. A printhead system
20 comprises the printer controller 10 and the printhead 1, which
is controlled by the controller. The printer controller 10
communicates dot data to the printhead 1 for printing.
A suitable type of printer controller, which may be programmed
accordingly, was described in our earlier patent application U.S.
Ser. No. 10/854,521 filed May 27, 2004.
It will, of course, be appreciated that the present invention has
been described purely by way of example and that modifications of
detail may be made within the scope of the invention, which is
defined by the accompanying claims.
* * * * *